During the installation of pile foundations for offshore wind farms (OWF) in the German North Sea, hydro sound emissions occur which are harmful to marine life. Limiting values defined by German authorities could not be met by the use of single noise mitigation systems (NMS) in past wind farm installations with large diameter monopiles. To improve noise reduction, combinations of several NMS are used in recent projects. Different NMS taking affect in different frequency ranges can reduce noise caused by impact driving more effectively. During offshore measuring campaigns at an OWF in the German North Sea, hydro sound measurements have been carried out in 7 distances from 15 m to 1500 m and in 5 depths from 1 m to 17 m over ground simultaneously. Results of these measurements will be shown in the time and frequency domain. Pile driving noise emissions with single NMS and combinations of NMS will be compared with reference measurements without NMS to evaluate different setups. The influence of the subsoil will be discussed as well as it has a significant influence on hydro sound propagation in general and the effectiveness of NMS in particular.